David Auburn spent about two years writing his new play, “The Columnist,” the longest writing process he’s ever experienced on a project. But it started out as just curiosity in the Vietnam War.

“I basically knew nothing about this part of our history and I wanted to learn about it,” Auburn said. “So I started reading a lot, and the name, Joe Alsop, pops up in histories of Vietnam.”

“The Columnist” is about the life of Joseph Alsop, the influential political journalist who ran in powerful D.C. circles and was a strong supporter of the Vietnam War.

“It was clear that he was a very influential, very famous journalist at the time, which is interesting because he’s now so obscure,” Auburn said. “I got interested in that question of how do you go from being a central, authoritative voice to being almost forgotten?”

In the production, which opens on Broadway tonight at the Samuel J. Friedman Theatre, John Lithgow stars as Alsop, while Boyd Gains plays Alsop’s brother Stewart, and Margaret Colin plays Alsop’s wife, Susan. The play is directed by Daniel Sullivan.

Auburn, who won the Pulitzer Prize for his 2000 play, “Proof,” has since written film screenplays, “The Lake House” and “The Girl in the Park,” and directed the latter as a film, but he’s been happy to return to theater. Speakeasy caught up with the playwright by phone to discuss his new work.

After “Proof,” you worked on screenplays and directing. Were you eager to return to playwriting?

I never really left playwriting, because I did do projects in the theater between then and now. But yes, I love playwriting. It’s where my heart lies and I was always eager to get back into the theater. I did a number of different projects, they weren’t all original plays but were one-acts or adaptations. Then I wrote a play that I never had produced and sort of never got out of my desk drawer, and I wrote this play, so I was always working.

How has it been working on “The Columnist”?

It’s just so satisfying to work in the theater. The artistic rewards are so profound. You have the pleasure of collaborating in the rehearsal room with the directors and actors, and then you have the experience of the audience response in the Broadway theater. It’s a completely different experience than anything else to have 700 people in a room listening to your work, responding in real time. There’s nothing like it for a writer.

How did you approach writing about Joe Alsop?

A lot of the early writing of the play was just about experimenting and trying to figure out what the scope of the play should be, how much time it should cover, what aspects of his life and of the era should I try to incorporate into the play. The biggest discovery was that I needed to cast the net as wide as possible, I needed to cover as much time as possible, bring in as many elements of his life and of the era as I could, so that I was writing a play about the man and his time, and doing that in a way that had the greatest scope that I could accommodate in the story.

Did you take liberties with Alsop’s character?

I don’t think I took any liberties with his character. I felt very strongly that the main job was to try to capture as many aspects of him as I could. He was such a complicated person with so many contradictions inherent in his life and in his behavior. He was so many different things to so many people that I felt the job was to get as much on stage as possible. I also felt there’s a tragedy in his life in that this immensely talented man was consumed by his own obsession, and that that leant a kind of natural arc to the story. The places I took liberties were more with chronology and imagining things that obviously no one witnessed and that required license to imagine, like the encounter in the hotel room. In terms of his character, I feel I’ve tried to stay very close to what I learned about him from the sources.

The structure of the play is unique. How did you decide what to show through scene and what to tell later, through dialogue?

Well, I had all these incidents and I was experimenting with different kinds of chronology. At a certain point I realized, if you tell the play chronologically, there’s an opportunity to withhold one piece of key information in each scene, and then reveal it in the next scene. You have a kind of interlocking structure so that at the end of the first scene, you don’t quite know what has happened, but you discover that in a couple scenes later. At the end of the Georgetown scene, you don’t know exactly what happened, but you find out that Kennedy came that night. So that structural idea helped me really solidify the play.